Conventional electric portable circular saws have a shoe for engaging and supporting the saw on a work piece for cutting. An upper guard is fixed to and extends above the upper shoe surface and covers an upper portion of the blade. A lower guard is pivotally mounted relative to the blade axis of rotation and is rotatable between an extended position for covering a lower portion of the blade which extends through the shoe and a retracted position for exposing the lower blade portion for cutting. The lower guard has a smaller diameter than the upper guard and is retractable within the upper guard when the lower guard is moved between its extended position and its retracted position. The lower guard in the extended position and relative to the blade feed direction has a leading edge and a trailing edge. In the retracted position of the lower guard, the trailing edge is located within the upper guard forwardly of the blade axis of rotation and generally disposed above the intersection (during cutting) of the blade tip with the workpiece ("cutting site"). When cutting, chips are propelled upwardly from the cutting site into the upper guard and flow through a chip flow duct defined by and between the upper and lower guards. For optimum operation, chips must flow freely and cleanly through the chip flow duct.
In certain types of these conventional circular saws which are designed for the European market, poor chip flow has been found to be a particular problem. One reason which is believed to contribute to the poor chip flow is that such saws are commonly equipped with a riving knife which rides in the kerf. The knife is mounted in the region adjacent to the upper and lower guards of the saw and restricts the available volume for the central and rear portions of the chip flow duct. A second reason is that in circular saws having a depth of cut pivot in the front of the saw, the pivot assembly also restricts the available volume for the front portion of the chip flow duct. A third reason is that European safety regulations limit the size of the openings and clearances for the upper guard and thus require the chip flow path to be somewhat restricted. Lastly, in certain cutting conditions such as the cutting of wet, soft wood, the generation of elongated wood chip or strands is prevalent during cutting. This is particularly true in Europe where lumber is not kilned dried as it is in the United States. The longer chips or strands have greater difficulty flowing through the duct.